I did the multiengine commercial instrument ride with Clyde Shelton through the ATP at Fulton County Apt. in Atlanta. Straight, no punches. Learn the "smacfum" acronym and be able to explain it with a sentence or two per letter. No tricks on the oral. Also I took the King Schools "Cleared for Multiengines" course to get ready, as well as read the FAA 8083 Airplane Flying Handbook section on multiengines before going to ATP. Good luck.